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Research Methods Test #2September 29 th , 2011 The Nature of VariablesVariable- A variable is an event or behavior that can assume at least two valueso For example: at least two different kinds of chairs in the room. Hair color, height weight. As long as there is more than one category it works.o Operational Definitions Brigman (1927) suggested that researchers should define theirvariables in terms of the operations needed to produce them. The spanking study was problematic because the researchers didn’t specify what the degree of spanking was. Specific definitions need to exist. Definitions allow others to replicate your studyIndependent Variables (IV’s): what is being manipulated.- Physiological IVo Conditions that alter or change the biological state of the participanto Example: temperature, drugs, food, alcohol, sleep deprivation- Experience IVo Manipulation of the amount or type of training of learningo Example: Memory, conditioning, teaching someone or something to do something- Stimulus or environmental IVo An aspect of the environment that the experimenter manipulates.o Example: basically everything else, changing music which would change your environment.Participant Characteristics:- Aspects of the participants, such as age, sex or personality traits, that are treated as if they are independent variables.o They are not true independent variables because they cannot be manipulated by the experimentero What type of studies use these pseudo independent variables? Post facto studies.o Dependent Variables: what is measures? Correctness Correct vs. Incorrect Rate or Frequency: separate but same ideaRate of Frequency: how quickly do participants respond in a certain time period.(in a 5 minute period the rat hit the bar 60times per min) Frequency: The number of responses or events that occur within a specified time period (number of times children interact during free play).- How many times the rat hits the bar in an hour. Degree or AmountSingle number, quantifies something that is not normally quantifiable (level of life satisfaction; self esteem score)Latency or Duration- Latency:)how quickly did the Ss make a response ( .15 sec to respond to an image on the screen)- Duration:how long did your response last (held the key down for 30 sec.)Nuisance Variables- Unwanted variable that can increase the range of the DV scores, but does not impact the levels of the IV differently.- Differences between the levels of the IV become more difficult to detect both visually looking at data and with statistical techniques.- Effects fall equally on all levels of the IV which is different from extraneous which impacts mean of one level compared to another level of IV.- Scores spread out because peoples score change (flatten out) because of the nuisance variable, range of scores spreads out, makes it less clear where the differences between two groups are.o For example: an experimenter has one group read a list of 10 neutral words and the other group reads 10 synonyms for slow. Then they measure the reaction time in participants on a task. Participants rangein age from 12-78.o Nuisance Variable- the age because their reaction time is affected by their age.o For example: one group is asked to count letters in the words while being shown words on a slide, and the other group puts the words in asentence while being shown. Then measure the ability of participants to recall a list of words. All groups are studied in a room with a noisy elevator.Nuisance Variable: Noisy elevator could distract the participants. Attention- some may be affected and some may not.- For example: One group is given a shot of epinephrine and one group is givena shot of a placebo then measured manual dexterity in room with frequent unpredictable change in temperature.- Nuisance variable: frequent Unpredictable changes in temperature.Getting better or worse could depend on the temp. Could do better or worse regardless if they got the drug or not.Tuesday, October 4 th , 2011 Controlling Extraneous VariablesGOAL: Produce groups that are equivalent prior to introduction of the independent variable, eliminate extraneous variables, and reduce the effects of nuisance variables as much as possible.Randomization: ensures that each participant has an equal chance of being assigned to any group in an experiment.- Example: level of motivation—we want equally motivated people in each experimental group.- DRAWBACK: You can never be fully aware of the variables that technique controls so oyu don’t know how effective its been.Elimination: EV’s are completely removed from an experiment.- Example: facial expressions across cultures (they’re the same.Constancy- EV is reduced to a single condition that is experienced by all participants (no longer a variable, only one level).o Situation: Juan and Nancy are interested in which teaching method is best for teaching stats. There are 2 classes and Juan will teach one using Method A and Nancy will teach the other using Method B.o What is the problem? We can’t tell whether the difference is due to the IV (the method) or the teacher (the DV)o How can we solve this problem using constancy? Only use one teacher—only has one value or level.o Controls for nuisance variables as well. Testing conditions and participant conditions are the same they shouldn’t have a wide spread of scores.Balancing: achieves “group equality” by equally distributing EV’s to all groups.- Situation: Juan takes 25 students and uses Method 1, then Juan takes 25 other students and uses method 2. Nancy takes 25 students and uses method1 and Nancy takes 25 other students and uses method 2.- The idea is that each teacher is now teaching both methods so the EV (if any exist) is evenly distributed.Counterbalancing: controls order effects by presenting different treatment sequences.- “Cola challenge” example: Cola A is tasted then Cola B is tasted.- We use the same taste cups, pour from the same type of container for both colas, everyone gets the same amount, and then we blind fold subjects.o EV’s are controlled with constancy and elimination.- What’s the problem?Order effect: always tasting A before B could skew results.CounterbalancingWithin-subject counterbalancing- Presentation of different treatment sequences to the same participant.- Drawback: each subject must experience each condition


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FSU PSY 3213C - Test #2

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